01-02 ACR Shock Evaluation Question

[natsfan]

I'm on the hunt for a Viper GTS. I am seriously considering an ACR. People have informed me about issues with the shocks on the 01-02 models. If I do decide to get a 01-02 ACR, what is the best way to evaluate the shocks and determine if they need to be rebuilt? What visual signs can I look for to determine if the shocks need to be rebuilt?

If I do get an ACR, I plan to swap the rear springs for a softer set. Where is a good place to get softer springs?

Thanks for the help.

 

[NI-KA]

Well opinions run rampant with regard to these shocks. The biggest complaint is that they leak. You can check the damper reservoir pressure with a gauge.

I bought a set. I got them because I was taking the car to the track and they were a good value compared to buying Motons (MCS today) or Penskes. I have since moved onto Penskes since I found a good deal on a used set which I sent back to Penske to get rebuilt. Still have the Dynamics , haven't got around to putting them up for sale.

They can be rebuilt just like Penskes or Motons. It is not unusual for a racing shock to get rebuilt.
There is one vendor in particular who is very fond of telling people that the stiff springs will put you at greater risk on washboard roads. Maybe? Maybe not?

Fact is (this comes from someone who built and raced these back in the day) these cars like a real stiff spring since it reduces body roll. It was counter intuitive at the time but when the racers started using stiffer spring rates lap times went down. So the implication is that if you are going to track the car, which was what the ACR moniker suggests then this should be a good thing.

The ACRs also had a different oil filter adapter that bypassed the filter during hard acceleration preventing oil starvation.

There are a number of vendors that can provide softer springs. They advertise here..... you won't have any trouble finding a reputable dealer.

 

[NI-KA]

Oh yea there were two different manufacturers used for the ACR. Not sure what years for which.

1. Dynamics
2. ?

I am sure someone will identify the years and other manufacturer.

 

[mitchdob]

ACR - 1999 to mid-2000: Koni
Mid-2000 through 2002: Dynamics (DS)
..... thanks to Camfab for that info.

I have a mid year 2000 ACR (built May 2000) with Dynamics. They've been great/strong, no issues.... though I haven't tracked the car.
As a note: the spring rates with the DS are ​50​​0 lbs/​front and ​1100 lbs/​rear.

 

[Dom426h]

Stock Springrates: 250front/450rear
1999-2000.5 ACRv1Koni...400 / 750
2000.5-2002 ACRv2DSI... 500 / 1100

Looking at a 2000 the DSI's are easy to spot sice they are blue&gold. I forget what color the Konis are. Inspecting, you can look for leaks down the shock body that road grime would likely be stuck to but its hard to tell for sure unless you yank all of em and test on a shock dyno. The seller could detail the suspension and you wouldnt know the difference... The konis rattle on some cars but i dont see that as a big deal as long as they function properly. The DSI's have the ridiculous spring rate that many swapped out. Both are considered "race" shocks that may require regular rebuilding that some people are not comfortable with.

IMO, Forget about the stock ACR stuff. Just replace it with KW, MCS or Penski right off the bat. Why settle for a 15yr old sub-par stock design(sorry srt) when you can have a current well designed top-knotch system.
Actually, IMO, Forget about the ACR in general. Just pick the color & year GTS that you want, put wheels on it that you like, and do the KW, MCS, or Penski dampers. Want an ACR sticker for the pose factor? That can be added as well.

 

[natsfan]

All,

Thanks for the replys. They have been helpful. I have gone back and forth between wanting to get an ACR. Right now, I'm back on the kick of getting an ACR. I want to keep the car as stock as possible and like the idea of the car coming from the factory ready for the track. I also have to admit I do like the idea of the car being rarer because it's an ACR. I plan to keep the car for a long time and wonder if the ACR would make it more collectible. I probably shouldn't be worrying about this and get a non-ACR, but sometimes desire beats logic.

 

[luc]

Quote "The ACRs also had a different oil filter adapter that bypassed the filter during hard acceleration preventing oil starvation.

completely wrong.
On a non ACR car, a control valve shut off oil flow to the cooler when oil pressure is below 30psi. (was mostly done for A/C reason)
On a ACR there is no control valve so less restriction and oil always flow through the cooler

 

[NI-KA]

So the oil filter adapter is the same in the ACR and non ACR ? I thought the valve you speak of is part of oil filter adapter?

 

[Dom426h]

completely wrong.
On a non ACR car, a control valve shut off oil flow to the cooler when oil pressure is below 30psi. (was mostly done for A/C reason)
On a ACR there is no control valve so less restriction and oil always flow through the cooler

+1 it just has to do with bypassing the flow from the oil cooler

add to that with the slight amount of flow increase without the valve(acr) i think youd be More likely to run out of oil in a long high-G corner. Think about it... On a 8second turn, would you rather have 100psi for 6seconds then 0psi for the last 2 ?, or 90psi for the full 8 sec ?
(I dont know the actual #'s, just threw something out there for a relatve comparison, and maybe its not even enough of a diff to worry about...)

Either way, the only way to prevent starvation for sure is to drive like the OP or to make sure you have the higher capacity oil pan and install the trap-door baffles.

 

[NI-KA]

http://forums.viperclub.org/threads/661577-Is-anyone-running-the-ACR-oil-filter-adapter-on-a-Gen-2.?highlight=ACR+oil+filter+adapter

 

[JonB]

I am a student of the Gen 2 ACR and its trivia. I even have the simultaneous GT-2 / ACR press kits of the day, with 35mm slides! The fully documented #0001 ACR 1999 Red/Silver is here in my town, with its original owner.

I invite your call.

The absolute FACT of the 2000.5 - 2002 ACR rear DSI shocks is that they were/are significantly over-sprung. On wasboardy roads, especially down hills, the ACR WOULD SKITTER ACROSS THE LANE! Scariest Viper I ever owned of 15+

I had a "bad" exchange of conversations with an engineer in MI over this issue. Almost a melt-down, and the ONLY disagreeable guy Ive ever met at Team Viper! Team Viper later sent an engineer from the AZ proving grounds to PIR to 'inspect-test' my 2001 brand-new ACR back in the day. He was doing other tests in NW. And he essentially agreed that the valving was impossible / ineffective to adjust because of the 1100 lb rear springs! Springs capable of handling GTS-R downforces, were toooooo powerful for a non-aero ACR. And they were ALL non-aero. So we re-sprung my ACR....and about 200 more to date. 100% happy owners, and safer on rough roads too.

Yes, DSI shocks can be rebuilt at several places in US and 1 in Canada and 1 in UK. Probably more. And, the vast majority of them WILL need rebuilding, especially if low-low-miles, or lots of track miles. Seeping / weeping / leaking is the first clue. 99-00.5 Konis are far less trouble, but were called "rattlers" since they did not have helper springs on them and would rattle annoyingly at negative G whoop-dee-doo roads.

The OE springs are so stiff on 00.5-2002 that many non-tracking ACR owners are unknowingly riding around on springs and degraded shocks. No problem for the show-car-cruiser set.

Other notes: The ACR Oil Filter adapter eliminated the "shuttle valve" of Non-ACRs. The valve STOPPED oil cooler flow at low speeds and lower RPMs. It let the oil run hotter! Why? To make the A/C system more effective. It was a (bad) trade-off for tracked cars, and it also resulted in lower oil PSI at idle and lower RPMs. So Team Viper dropped the valve for all ACRs.

And many tracked-cars learned of this mod RIGHT HERE, and retro-fit it to their non-ACRs. [A Team-Viper engineer very much wanted VIPER DAYS COMPETITORS to know about it, and announced it here, under a pseudonym!] An immediate 5-7 PSI gain resulted at idle., and cooler oil since the cooler was fully inline at all times. PSI at speed was 3-5 PSI higher. A Good Mod.

Trivia: 92-94 Vipers did not have this shuttle valve. Why? No AC in most of em. When they got AC in 94.5+, the valve debuted to help minimize heat on the AC system.